Rift in the Larsen C ice shelf photographed by NASA’s IceBridge aerial survey in November 2016. Image: NASA/John Sonntag

A 80-mile-long crack along Antarctica’s Larsen C Ice Shelf has remained stable since February, but scientists have now detected a new branch, one that’s extending about six miles from the main rift. It seems like only a matter of time before the 2,000 square mile ice shelf plunges into the sea.

Geologists with Project MIDAS, a UK-based research project studying the effects of melting on the Larsen C ice shelf, have been monitoring the crack for several years now, but the rift experienced a sudden growth spurt this past December when it grew by 12 miles (20 km). In January, the crack advanced another six miles (10 km) over the course of two weeks. The Larsen C Ice Shelf is fully expected to collapse, or calve, at which time it will lose more than 10 percent of its ice surface area (a region roughly the size of Delaware). The latest observations suggest this monumental event may happen sooner rather than later.

The current location of the rift on Larsen C, as of May 1 2017. (Credit: Project MIDAS)

A report from Project MIDAS shows that, as of May 1, 2017, a new branch has appeared along the rift. The fissure emerged about six miles behind the tip of the main channel and is heading towards the ice-front. “This is the first significant change to the rift since February of this year,” write the geologists.

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It’s winter in Antarctica, so direct visual observations are hard to come by. Researchers with Project Midas used the synthetic aperture radar (SAR) interferometry instrument aboard ESA’s Sentinel-1 satellites to make the observations.

Ice flow velocities of Larsen C in February 2017 and April/May 2017, from ESA Sentinel-1 data.

The main rift’s length hasn’t changed over the past several months, but it has been steadily widening—sometimes by as much as a meter per day. “This widening has increased noticeably since the development of the new branch, as can be seen in measurements of the ice flow velocity,” write the Project Midas scientists. This would suggest that the integrity of the ice shelf is becoming increasingly unstable.

The warmer air and water in the region is largely driving the changes to the region’s ice; the main crack now measures about 1,500 feet (450 meters) wide. No timetable has been set for the all-but-inevitable calving, which will be one of the largest such events on record, although as we’ve explained before, it won’t contribute to sea level rise directly. But the new fissure shows how quickly the situation is changing, even as winter sets in.

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[Project Midas]